1. Field of the Invention
The present invention is directed to formulations for use as sulfur scale removal and inhibition agents in the treatment of pipelines and other water processing equipment used in various industrial water systems, for example including but not limited to geothermal energy production cooling towers, secondary oil recovery systems, Frasch process sulfur mining, and industrial cooling towers.
2. Description of Related Art
The presence of sulfur in industrial water systems has posed many problems, such as corrosion of the pipes, blockage of the flow of the liquid, slurry or gas through pipes, and loss of efficiency in the transport through the system, including heat transfer. In geothermal systems, sulfur deposition is particularly problematic as the sulfur deposits build up on the spray nozzles in cooling towers (see for example FIGS. 1 and 2) that are an integral part of electricity production that consists of geothermal steam pressure to drive electricity producing turbines.
The sulfur deposition in a water distribution system in geothermal applications causes the subsequent fouling of heat exchanger elements of the electric utility. In particular, sulfur deposit formation on the surfaces of the cooling tower “packing” or “fill” thereby causes low flow or total blockage of water flow in the cooling medium (see FIG. 3).
The low flow or no flow condition caused by these sulfur deposits in turn facilitates the buildup of organic deposits. These organic deposits are composed predominantly of polysaccharides and proteins which are generated by microorganisms, in particular slime producing bacteria. Therefore the control of sulfur deposition is essential as it is the first step in a series of processes that lead to inefficient operation of the electric power plant. If these deposits build up in the cooling tower fill, the entire physical structure can collapse, which is not an uncommon occurrence. Clearly, at the very least such an event is a costly repair with loss of electrical output.
In addition, the Frasch process for sulfur mining involves processing of sulfur with hot water. Such a system also benefits from sulfur deposit removal in the piping and equipment, thus aiding in plant operations.
With regard to iron sulfide as a sulfur deposit, its presence in industrial water systems has posed many problems, such as under-deposit corrosion of the pipes, blockage of the flow of the liquid, slurry or gas through pipes, clogging of filtration systems, and loss of efficiency in the transport through the system. In particular, the control of iron sulfide deposition in the piping of oil production is key to the efficiency of oil production. These iron sulfide deposits can not only be blocking to water flow and oil flow, but the piping can corrode or deteriorate to the point that a new producing well or return water well has to be drilled or repaired. These events can be expensive and time consuming to repair. Iron sulfide deposits may result not only from corrosion of iron-containing materials of construction, but from reaction of iron and iron compounds that occur naturally in the water system with hydrogen sulfide or other sulfur compounds.
Once the sulfur scale has formed, mechanical treatments to remove sulfur deposits from these industrial systems have used scrapers, sponge balls or “pigs” and various chemicals. These methods cause the sulfur deposit to be loosened and further contaminate the system in other locations in the system. Also various chemical methods have been tried but nothing to date has met with commercial success.
U.S. Pat. No. 5,025,038 describes an antimicrobial composition for use as a biocide where the active ingredient is 2-(alkylthio)ethanamine hydrohalide. The patent describes a formulation for use as a biocide. No other use is taught. U.S. Pat. No. 4,982,004 describes a process to make the compounds of U.S. Pat. No. 5,025,038.
U.S. Pat. No. 4,816,061 describes a composition to control biofouling using alkylthioalkylamines, such as n-decylthioethylamine, and its hydrochloride salt. The active is used as a biocide. The composition is not used or taught for sulfur scale removal.
U.S. Pat. No. 3,524,719 describes organic amines combined with N,N″-(hexachlorobiphenylene)bis(ethylenediamine) or 1,1′-(hexachlorobiphenylene)-bis(ethylenediamine) for use in inhibiting metal corrosion. There are no salts of these amines discussed. These compounds are used for corrosion inhibition only. Removal or dispersal of corrosion products such as iron sulfide from surfaces is not taught by this patent. Inhibition of iron sulfide deposition from reaction of naturally occurring iron with sulfur compounds also is not taught by this patent.
U.S. Pat. No. 6,260,561 describes the use of aliphatic amines for cleaning swimming pools and spas. The focus of the patent is the problem of flocculus or deposits resulting from dissolved minerals in swimming pools, spas, or other receptacles holding water. Also taught is antimicrobial activity. It teaches that a thioethylamine analog has inferior performance compared to their claimed aliphatic compounds. The prevention or removal of sulfur deposits is not taught.
WO 2005/014491 describes etheramines and their nitriles for water treatment for use as biocides of sulfate reducing bacteria (SRBs) as well as other problematic aerobic microorganisms in oilfield applications and in industrial water systems, although they do not show any support for these latter uses. SRBs produce H2S from sulfates. H2S is a problem due to odor, toxicity, and corrosivity. The presence of H2S leads to plugging of lines by the formation of and precipitation of metal sulfides. This problem, the formation of H2S by bacteria, is commonly treated with biocides that kill the bacteria or prevent the bacteria from producing H2S. This reference does not teach inhibition or removal of elemental sulfur deposits; however, it teaches how to kill the bacteria. Additionally, there is no teaching of iron sulfide removal or dispersal.
S. Watanabe, et al., in J. Amer. Oil Chemists Soc. 68, 44-46 (1991), describe the testing of amines as a component of aqueous cutting fluid used in metal machining operations that showed excellent corrosion resistance of iron, excellent lubricity (wear resistance), and fair antimicrobial properties in spent coolant solutions. There was no discussion of sulfur deposit removal or inhibition.
U.S. Pat. No. 3,291,683 describes controlling fungi and bacteria with alkoxy or alkylthio alkylamine ethers. This patent's focus is biocide use.
U.S. Pat. No. 4,032,360 describes diamines with a carbon chain derived from a higher fatty acid for use in iron sulfide removal in oil-containing systems. It was not used in industrial water systems. There was no discussion of sulfur deposit removal or inhibition.
S. Kudo and T. Yano in Proceedings World Geothermal Congress 2000, Kyushu—Tohoku, Japan, May 28-Jun. 10, 2000, pp. 3205-9 describe the use of a sulfur scale abatement system using a surfactant in geothermal power plant circulating water. The composition of the surfactant was described only as a “common industrial, anti-bacterial reagent.” There is no further disclosure of the reagent.
Clearly, it would be desirable to find a formulation that would prevent sulfur deposit formation and permit the substantial removal of sulfur deposits from industrial water systems and pipelines.